Electric motor.



No. 762,709.- PATENTED JUNE 14, 1904. G. c. HALL. BLEGTRIO MOTOR.

APPLIOATION FILED MAR. 7, 1901.

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No. 762,709. PATENTED JUNE 14 1904. G. G. HALL.

ELECTRIC MOTOR.

APPLICATION FILED-MAB. 7, 1901.

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Patented June 14, 1904.

GAYLORD C. HALL, OF NEIV YORK, N. Y.

ELECTRIC MOTOR.

SPECIFICATION forming part of Letters Patent No. 762,709, dated June 14,1904.

Application filed March 7, 1901. Serial No. 50,228. (No model.)

To all whom, it may concern.-

Be it known that I, GAYLORD C. HALL, of the city, county, and State ofNew York, have invented a new and useful Improvement in Electric Motors,of which the following is a full, clear, and exact description whentaken in connection with the accompanying drawings, which form a partthereof, and in which Figure 1 represents a diagram of an electric motorand associated parts embodying my invention, and Fig. 2 a modified formof the same.

In both figures similar letters of reference represent like parts.

This invention relates to electric motors, and more particularly to themethod of and construction for speeding up the motor; and it consists inautomatically varying the resistance in the circuit in which the motoris located by the utilization of the increased difference of potentialor rise of voltage aroun the motor as the speed of the motor increases,the invention being herein described as applied to the gradual speedingup of a motor by decreasing the initial or st rting resistance throughthe actuation of certain devices upon the increase of voltage around themotor through the presence of the back electromotive force generatedupon the acceleration of the motor, as more fully set forth and claimedhereinafter, together with minor improvements and combinations of parts.To this end a secondary or supplementary circuit is shunted around themotor, which as the potential around the motor is increased actuates thedevices or apparatus for cutting out or decreasing the resistance orresistances (in the form of rheostats or otherwise) located in the maincircuit.

Referring to the drawings, the letter L represents the main line orcircuit, and M the motor in said circuit.

R R I'I R", &c., represent a number of rheostats or resistances locatedin the main circuit, the particular form or arrangement of which may bevaried. The main circuit L is provided with a plurality of switches T TT T, &c., having contact devices Q Q Q Q, &c., so located in relation tothe resistances R R R R, &c., that the making or breaking of each switchvaries the strength of the resistance in the main circuit. These contactpieces or devices for varying the resistance in the main circuit areactuated by the rise of voltage around the motor by the followingmechanism, which is a simple and preferred construction, although theinvention is not intended to be limited thereto: A secondary circuit,herein called the positive-action circuit A, is shunted around the motorH, not around the resistances R R R", &c., and in this circuit A arelocated one or more solenoids or coils S S Si &c., each of whichactuates a plunger 1 F 1 &c., or other suitable device. Each plunger isshown connected at one end with one of the contact devices Q Q Q, &c.,for closing one of the switches T T1, 850. By the variation in thenumber of turns of wire in the different coils S S S", &c. the currentnecessary to actuate one plunger, such as P, may be less than thatnecessary to actuate another plunger, as P", so that the plungers willbe actuated successively as the current in the positive-action circuitAincreases, the increase corresponding to the increase of potentialaround the motor M. By this means as the voltage around the motorincreases the contact-pieces Q Q Q, &c., will be successively actuatedto close their respective switches T 'I T &c., and this action willdecrease the resistance in the main circuit.

The main circuit is first made by the switch T, which is herein shown ascontrolled by a controlling-circuit C, in which is located astarting-switch X. In the controlling-circuit C is located a solenoid orcoil S, which actuates a plunger P, having connected therewith thecontact device Q for closing the switch T. When upon the closing of thestartingswitch X the plunger P s actuated by the coil S and the contactdevice Q closes the switch T, the motor is started with its initial orstarting resistance. As its speed increases by the back electromotiveforce generated thereby the voltage around the motor is increased overthat present on starting, and the current in the positive-action circuitA is correspondingl y increased. Thisincrease of current in thepositive-action circuit A is sufficient to actuate one of the plungers,such as P, through its corresponding coil S (this coil having thegreatest number'of turns of any of the coils in the positive-actioncircuit,) and by the operation of the plunger P the contact device Qcloses the switch T and the resistance in the main line thereby isdecreased, as indicated. Upon this decrease of resistance in the maincircuit the speed of the motor is increased, which, with the furtherback electromotive force thereby developed, increases the voltage aroundthe motor and the positive-action circuit A, so that another plunger, asP, is actuated by its coil S and the switch T is closed, tending tofurther reduce the resistance in the main circuit. The operation may berepeated with successive plungers until the resistances are reduced to aminimum and the maximum speed of the motor obtained.

A switch T is provided to make or break the positive-action circuit C.Upon closing the switchX a plunger P, connected to a contact device Qfor closing the switch T, is actuated by a solenoid or coil S, locatedin the controlling-circuit C, so that when the starting-switch X isclosed the positive-action circuit A is thus closed and remains so untilthe switch X is opened. When the switch X is opened, the circuit A isbroken, which allows the plungers P P P, &c., to fall, thus opening theswitches T T T*, &c. As described above, the coil S is also controlledby the switch X, so that when the switch X is opened all the switches inthe main circuit are opened, thus stopping the motor.

In Fig. 2 is shown a modified form of the invention embracing a furtherimprovement whereby the contact pieces or devices for varying theresistance are actuated not merely by the increase in voltage around themotor, but by the relation of this voltage to or its difference fromthat around the resistances. To this end a circuit, herein called theretarding-action circuit A, is shunted around the resistances and haslocated therein solenoids or coils V V V*, &c., each acting upon one ofthe plungers P P P*, 620., but in the opposite direction from thesolenoids or coils S S S &c. By this means each of the plungers P P P,&c., is acted upon by two coils or solenoids, respectively, as S an d VS and V S and V*, &c., of which that in the positive-action circuit Atends to shift the plunger and contactdevice to close the switch T T T,&c., while that in the retardingaction circuit A tends to hold theplunger and contact device away from the switch. As indicated by thenumber of turns in the various coils, one of the positive-action coils,as S may be arranged to require less current to shift its plunger byovercoming the action of its corresponding retarding-action coil V thananother coil, as S in overcoming its corresponding retarding-action coilV. This difference may be accentuated by varying the ratio of the turnsin the different retardingaction coils V V Vi &c., to those of theircorresponding positive-action coils S S 8*, &c., to suit the conditions.With this construction the voltage around the motor need not beincreased to any certain amount to operate all the plungers, but needmerely attain a certain prescribed relation to that around theresistances, or, in other words, irrespective of what the exact voltagein the main circuit be (within certain limits) when acertainfractionalportion thereof is around the motor, with the remainder aroundthe resistances, the severaldevices for decreasing the resistance willbe actuated.

In case a shunt-wound motor were used the positive-action circuit wouldbe shunted around the armature of the motor.

Having now described my invention, (which may vary in its detailswithout departing from the spirit thereof,) what I claim, and desire tosecure by Letters Patent, is

1. The combination with amain circuit containing a motor and aresistance; of ashunt circuit containing the starting-switch; and apositive-action circuit shunted about the motor and closed and broken bysaid shunt-circuit, substantially as described.

2. The combination with a main circuit containing a motor andresistance; of a shuntcircuit containing the starting-switch;apositiveaction circuit shunted around the motor and closed or broken bysaid shunt-circuit; and devices for varying the resistance controlled bythe current in said positive-action circuit, substantially as described.

3. The combination with amain circuit containing a motor and resistance;of means for varying the resistance oppositely actuated by thedifierence of potential around the motor and the difference of potentialaround the re sistance, substantially as described.

4. The combination with a main circuit containing a motor andresistance; of a positiveaction circuit shunted around the motor; aretarding-action circuit around the resistance; devices for varying theresistance oppositely actuated by the current in the positive-actioncircuit and the current in the retarding-action circuit, substantiallyas described.

5. The combination with a main circuit containing a motor andresistance; of a positiveaction circuit shunted around the motor; aretarding-action circuit shunted around the resistance; a series ofdevices oppositely actuated by the current in the positive-actioncircuit and the current in the retarding-action circuit, the successivedevices being actuated by diflerent degrees of strength in said curandshunt-circuit simultaneously, substanrents, substantially as described.tially as described. I 6. The combination Withamain circuit, con- InWitness whereof I have hereunto set my taining a motor and resistance;of a supplehand on the 4th day of March, 1901. 5 mental-y circuitshunted around the motor; GAYLORD (J. HALL.

devices for varying the resistance controlled Witnesses: by the currentin the shunt-circuit; and means LINCOLN A. STUART,

for making and breaking the main current HJALMAR WALLERS'IADT.

